The present invention relates to collection and analysis of liquid from a below-ground location for analysis.
There exist various types of installations in which it is necessary, or at least desirable, to collect a liquid from a location which is not readily accessible for analysis. To cite one example, it is known to be desirable, and in some jurisdictions mandatory, to assure that leachate from landfills and similar structures does not contaminate surrounding soil or water supplies.
To this end, it has been proposed to provide landfills with membrane liner leachate collection systems or pan lysimeters, i.e. essentially a large basin buried under a representative portion of a landfill to underlie a mass of waste material which has possibly been backfilled, or covered with soil. The membrane liner or pan lysimeter will catch water and waste material components which percolate through the overlying portion of the landfill and will direct the water and any contaminants therein, i.e., the leachate, to an outfall pipe forming part of the membrane liner or lysimeter.
If a collection device such as a membrane liner or pan lysimeter is provided in a landfill, some means must be provided to bring the leachate to an accessible location. It is already known to bury a caisson or tube in the ground down to the membrane liner or lysimeter outfall pipe. A portable collection vessel is placed in the caisson or tube to receive leachate from the outfall pipe. Depending on design, a worker must climb down into the caisson, perhaps once each week, to retrieve the collection vessel. The caisson must be constructed to provide a safe environment and breathable atmosphere for the worker and each trip to retrieve a collection vessel and to replace that vessel with an empty one requires a certain time. Therefore, this approach to leachate collection has a cost and health risks which are not insignificant.
It is known in other arts to convey liquid from a below ground location to the ground surface using mechanical devices such as, for example, pumps.
However, the leachate recovered for testing must correspond chemically and physically to the liquid reaching the membrane liner or lysimeter; otherwise it will not permit an accurate determination of the effect of the landfill on surrounding soil and water. The procedures described above, including the manual collection procedure, provoke degradation, e.g. oxidation, of the leachate, which will falsify the analysis results. The analysis results can be further falsified by precipitation of contaminants in a sample and other reactions.